This invention relates to a wireless interconnect for an integrated circuit, and a method for making a wireless interconnect for an integrated circuit.
Known integrated circuits (ICs) include a wireless interconnect having first and second antennae, between which electromagnetic (typically RF) radiation carrying a signal can be propagated. Typically, an IC having such a wireless interconnect may also include wired interconnects comprising a plurality of electrically conductive signal lines. An example of such an arrangement is shown in FIG. 1.
In FIG. 1, a first antenna 2 and a second antenna 4 are arranged over a plurality of electrically conductive (wired) interconnects indicated generally at 12. The first antenna 2 and a second antenna 4 and the electrically conductive interconnects 12 are provided in a region 6. The region 6 is provided on a substrate 8.
The arrangement shown in FIG. 1 suffers from the problem of interference in the signals passed between the first 2 and second 4 antennae, caused by the presence of the electrically conductive interconnects 12. This interference can lead to signal distortion and a loss of transmission gain.
Propagation of electromagnetic radiation between the first 2 and second 4 antennae in arrangements of the kind shown in FIG. 1 occurs primarily within the substrate 8. As can be seen from FIG. 1, radiation propagating between the first 2 and second 4 antennae via the substrate 8 must traverse the region containing the electrically conductive interconnects 12, whereby the electrically conductive nature of the interconnects 12 can lead to the aforementioned interference.
It may be possible to avoid overlap of the antennae 2, 4 with areas in the IC 10 containing electrically conductive interconnects 12. This could, for example, be achieved by placing the antennae 2, 4 and the wired interconnects in completely separate areas of the IC, or by leaving openings in the network of interconnects 12 (beneath the antennae 2, 4) to allow the free passage of electromagnetic radiation. Neither approach is desirable however, since they would both increase the complexity of the IC design and would create exclusion areas for the electrically conductive interconnects 12 leading to a loss of effective chip area.
A paper by Rashid et al. entitled “Interference suppression of wireless interconnection in Si integrated antenna”, Interconnect Technology Conference, 2002, Proceedings of the IEEE 2002 International, pages 173-175, describes 3-D finite element simulations of Si integrated antennae. The simulations described in this paper indicate that a rapid decrease in antenna transmission gain occurs when the number of signal carrying metal lines between the transmitter and the receiver is increased. The authors of this paper suggest placing a high resistivity Si or high permittivity interlayer dielectric material below the antenna, with the signal lines below the interlayer.
Embodiments of this invention can address at least some of the problems indicated above.